From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BF9EC43603 for ; Mon, 16 Dec 2019 19:07:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 034AB20CC7 for ; Mon, 16 Dec 2019 19:07:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726840AbfLPTHR (ORCPT ); Mon, 16 Dec 2019 14:07:17 -0500 Received: from mga09.intel.com ([134.134.136.24]:23800 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726368AbfLPTHR (ORCPT ); Mon, 16 Dec 2019 14:07:17 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Dec 2019 11:07:16 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,322,1571727600"; d="scan'208";a="212128531" Received: from chenyian-desk1.amr.corp.intel.com (HELO [10.3.52.63]) ([10.3.52.63]) by fmsmga007.fm.intel.com with ESMTP; 16 Dec 2019 11:07:16 -0800 Subject: Re: [PATCH 1/3] iommu/vt-d: skip RMRR entries that fail the sanity check To: Barret Rhoden , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , David Woodhouse , Joerg Roedel , Sohil Mehta Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, x86@kernel.org References: <20191211194606.87940-1-brho@google.com> <20191211194606.87940-2-brho@google.com> From: "Chen, Yian" Message-ID: <99a294a0-444e-81f9-19a2-216aef03f356@intel.com> Date: Mon, 16 Dec 2019 11:07:16 -0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20191211194606.87940-2-brho@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/11/2019 11:46 AM, Barret Rhoden wrote: > RMRR entries describe memory regions that are DMA targets for devices > outside the kernel's control. > > RMRR entries that fail the sanity check are pointing to regions of > memory that the firmware did not tell the kernel are reserved or > otherwise should not be used. > > Instead of aborting DMAR processing, this commit skips these RMRR > entries. They will not be mapped into the IOMMU, but the IOMMU can > still be utilized. If anything, when the IOMMU is on, those devices > will not be able to clobber RAM that the kernel has allocated from those > regions. > > Signed-off-by: Barret Rhoden > --- > drivers/iommu/intel-iommu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index f168cd8ee570..f7e09244c9e4 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -4316,7 +4316,7 @@ int __init dmar_parse_one_rmrr(struct acpi_dmar_header *header, void *arg) > rmrr = (struct acpi_dmar_reserved_memory *)header; > ret = arch_rmrr_sanity_check(rmrr); > if (ret) > - return ret; > + return 0; > > rmrru = kzalloc(sizeof(*rmrru), GFP_KERNEL); > if (!rmrru) Parsing rmrr function should report the error to caller. The behavior to response the error can be chose  by the caller in the calling stack, for example, dmar_walk_remapping_entries(). A concern is that ignoring a detected firmware bug might have a potential side impact though it seemed safe for your case. Thanks, Yian